Extract BranchMispredictDetection unit out of Mem module to a separate module

[pavelkryukov]

Currently Mem module handles two operations:

1. Loads and stores to/from data memory
2. Branch conditions check.

Actually mem should check only the first one, while the second one should be handled in a separate module.

[vodogrey2012]

Hello. I am going to try to solve this issue at the closest weekend. But now I have any common questions:

1. As I understand, I need to create new method. It means, I need to make new header file, wich contains one function branch_predictor and its cpp-file with realisation?
2. This header must be uncluded in mem module and brunc_predictor must be called in clock function, is it?
3. How can I test this modul?
   Thank you.

[pavelkryukov]

As I understand, I need to create new method.

No, it should be a separate class. Currently we have 6 modules located in simulator/modules:

• core (includes other modules)
• fetch
• decode
• execute
• mem
• writeback

The new module should be the 7th one. I advise you to start with copying Mem module and removing everything unrelated.

This header must be uncluded in mem module and brunc_predictor must be called in clock function, is it?

As the module is same-rank as mem, it should be called from core module clock:

mipt-mips/simulator/modules/core/perf_sim.cpp

Lines 76 to 84 in 0f4ab8f

	template<typename ISA>
	void PerfSim<ISA>::clock_tree( Cycle cycle)
	{
	writeback.clock( cycle);
	fetch.clock( cycle);
	decode.clock( cycle);
	execute.clock( cycle);
	mem.clock( cycle);
	}

How can I test this modul?

Run your bubble sort trace, for instance — it should demonstrate performance about 0.6 IPC if everything is correct. Additionally, you may create unit tests, but that's tricky with ports at the moment.